Does your motor take the full 15A this CT can handle, when it's running?
I would guess not, since I would not want to design anything without a bit of headroom, for safety.
If it takes rather less than 15A, then the CT will give less than 1v.
A single NPN transistor as described needs 0.6 - 0.7v on its base to start conducting, so you may find nothing much happens unless the motor takes a good proportion of that 15A - though since a motor can take a large current when starting, with the current dropping considerably once it's up to speed, you could get some wildly random results.
And also note, this is all AC - the motor current is AC, and so is the output of the CT - so there's negative voltages around as well as positive ones, and the Pi really won't like those.
Personally, I would feed the CT output into an amplifier such as a TL072; feed the output of that into a bridge rectifier; and use that to drive an optoisolator. That way, the Pi is isolated and kept safe.
That will need a separate power supply, with both positive and negative rails.
But before I did anything else, I'd want to know more about the motor!
JohnsUPS wrote: ↑
Tue Aug 27, 2019 10:13 pm
... It appears as though the CT transformer has a resistor in it, because the output is given as a voltage and not a current ...
That page gives "Build-in sampling resistance（RL): 124Ω".
Given that it's supposed to give out 1v for 15A input, that's about 8mA through 124Ω, and we can guess at about 2000 turns in the CT